The present invention relates generally to solid propellant formulations and to methods and devices employing the same for the destruction of airborne biological and/or chemical agents.
Propellants are chemical compounds or mixtures thereof which, upon ignition, exhibit self-sustained combustion and generate large volumes of hot gases at controlled, predetermined rates. Propellants serve as a convenient, compact form of storing relatively large amounts of energy and working fluid for rapid release and enjoy wide utility in various industrial and military applications. Thus, propellants are generally employed in various situations requiring a readily controllable source of energy such as ballistic applications (e.g., for periods of time ranging from milliseconds in weapons to minutes for space vehicles) wherein the generated gases function as a working fluid for propelling projectiles such as rockets and missile systems, and for pressurizing pistons and inflating containers.
When used as a propellant for rocket and missile systems, a propellant formulation is typically shaped as a cylinder, called a xe2x80x9cgrain.xe2x80x9d The propellant grain is combusted, typically at constant pressure within the interior of the rocket motor case. The rocket motor derives its thrust from the flow of the hot combustion products through the throat and out the nozzle of the motor case. Solid propellants are employed extensively in the aerospace industry for rockets and in the automotive industry for air bags. Solid propellants have evolved as the preferred method of powering most missiles and rockets for military applications and inflating air bags for civilian applications because they are relatively simple and economic to manufacture and use, and have excellent performance characteristics and are very reliable and safe.
It is known that propellants can be engineered so as to achieve desired burn rate characteristics. For example, U.S. Pat. No. 4,092,189 to Betts1 discloses that granules of ultra-high burn rate propellants may be dispersed in a binder or lower burning rate propellant to achieve desired characteristics. U.S. Pat. No. 5,682,009 discloses that a burn deterrent may be gradationally dispersed within the particulate with the greatest concentration of burn deterrent at the particulate periphery. According to U.S. Pat. No. 4,462,848, relatively higher burning rate casting powder granules are distributed uniformly throughout a cross-linked double base propellant composition.
1 This publication, as well as all other publications cited below, are expressly incorporated hereinto by reference. 
The potential proliferation of hazardous biological and/or chemical agents has revealed the need for defenses in the event of their possible use to be improved, especially in military theater of operations. Typically, defenses against air borne biological and chemical agents has been limited to protective clothing and breathing apparatus. A need therefore exists to provide improved defenses against the potential use of such hazardous biological and/or chemical agents.
Broadly, the present invention is embodied in a high temperature incendiary (HTI) device and methods which destroy biological and/or chemical agents. More specifically, the present invention is embodied in dual modal propellant compositions for use in HTI devices, and to such HTI devices employing the same, wherein the propellant composition is comprised of low burn rate propellant particles dispersed in a matrix of a high burn rate propellant. Most preferably, the HTI device includes a casing which contains the dual modal propellant and a nozzle through which combustion gases generated by the ignited high burn rate propellant may be discharged thereby entraining ignited particles of the low burn rate propellant.
In use, therefore, the high burn rate propellant will be ignited using a conventional igniter (not shown) thereby generating combustion gases which are expelled through the nozzle of the HTI device. As the ignition face of the propellant composition regresses, the low burn rate particles will similarly become ignited. Since the low burn rate particles burn at a lesser rate as compared to the high burn rate propellant in which such particles are dispersed, the ignited particles per se will be expelled through the nozzle and will therefore continue to burn in the ambient environment. Such continued burning of the particles will thereby be sufficient to destroy chemical and/or biological agents that may be present in the ambient environment.